1. Field of the Invention
The invention relates to plant nutriments encapsulated in synthetic lipid vesicles and to their use in agriculture to nourish plants.
2. Brief Description of the Prior Art
Plants, like animals, are nourished by certain nutriments in order to sustain their life. However, unlike animals, plants themselves manufacture the organic nutriments required for assimilation into protoplasmic materials, from more basic elements such as carbon, hydrogen and oxygen. More specifically the plant will itself manufacture the starches and sugars it requires for plant metabolism from carbon, hydrogen and oxygen taken into the plant structure. In addition to carbon, hydrogen, and oxygen, thirteen other elements have been identified as essential to plant nutrition. These are nitrogen and phosphorus (for protein synthesis), potassium calcium, magnesium, sulfur, iron, manganese, copper, zinc, boron, molybdenum, and chlorine. Although the latter elements may be taken into the plant body through the leaf structure, they are more usually taken in by the plant in the form of minerals, dissolved in water and absorbed through the plant's root system from the surrounding soil. These minerals as nutriments may or may not be found in given soils. When they are not, the agriculturist may resort to applying nutriment supplying compositions to the plant situs in the form of fertilizer compositions.
Plant nutrient or nutriment compositions such as commerical fertilizer compositions are of various types. Most of them contain water-disperable or water-soluble materials which can be assimilated by plants. Fertilizers are representative of such nutrient materials. The water-soluble ingredients, such as nitrogen, potassium and phosphorus compounds which are the most commonly used, are often too rapidly leached out of the fertilizer composition are carried away by surface and ground waters long before growing plants can gather and assimilate the nutritive elements. Hence, in many cases a large proportion of desirable nutritive elements is lost and to this extent the fertilizer or other nutrient is wasted.
Numerous attempts have been made in the prior art to reduce water solubility and the leaching rate of fertilizer and like nutrient materials, while at the same time not rendering them incapable of assimilation in growing plants. For example, a number of attempts have been made to incorporate small quantities of fertilizer in fairly high proportions of relatively water-insoluble carriers such as asphalt, resins, plastics, wax and the like; see for example U.S. Pat. Nos. 3,712,867; 3,778,383; and 3,321,298. In some cases the fertilizer ingredients themselves have purposely been made relatively insoluble. In other instances, granules or other small particles of the fertilizer have been coated with water repellent or water resistant materials including such as those named above. In general, these procedures have not been very effective. Thus, if the fertilizer particles are very highly waterproofed, they prevent assimilation by the plants of the needed fertilizer ingredients. If plastic hydrocarbon coating materials which retain a tacky or cold flow property, such as wax or asphalt, are employed, they tend to cohere and agglomerate unduly or to pack in large lumps during periods of storage.
Other difficulties that are encountered in applying fertilizers and like nutrients to soil are (a) neutralization of the materials by reaction with soil components, e.g., phosphate fixation, and (b) their destruction by microorganisms before they can be assimilated by the plant, e.g., the action of denitrifying bacteria.
Basic to the method of our invention is the use of plant nutriments encapsulated in lipid vesicles. When applied to a plant situs the encapsulated nutriments are released slowly at the plant situs over a period of time for absorption by the plant or they may be taken in by the plant in their encapsulated forms. The encapsulated nutriments remain fully bio-available for systemic plant nutrition when absorbed into the plant structure and this unique delivery of nutriments within the plant system may be advantageous in terms of nutritional efficiency.